Electrical control system for clothes dryer



April 23, 1957 l.. o. MAYHAN, JR 2,789,367

ELECTRICAL CONTROL SYSTEM FOR CLOTHES DRYER Fi1ed.Dec. 1-4, 1953 2 Sheets-Sheet l HOOOOO o 4 3- INVENTOR.

LEONARD o MAYHAN. JR. BY l ms ATTORNEY f C O f O O f O O O C O O O O G. T .Il a F m l\\l 8 April 23, 1957 1 o. MAYHAN, JR 2,789,367

ELECTRICAL CONTROL SYSTEM FCR CLOTHES DETER Filed Dec. 14, 1953 2 Sheets-Sheet 2 FIG. 2 f f3 IN V EN TOR.

BY if Hls ATTORNEY LEONARD O. MAYHAN. JR.

United States Patent 2,789,367 ELECTRICAL CONTROL SYSTEM FOR CLOTHES DRYER Leonard 0. Mayhan, Jr., Louisville, Ky., assignor to General Electric Company, a corporation of New York Application December 14, 1953, Serial No. 398,039 1 Claim. (Cl. 34-45) This invention relates to clothes dryers, and more particularly to an electrical control system for such machines.

An object of this invention is to construct a clothes dryer having definite and distinct operating temperatures for selection by the operator, so that the dryer may be employed as safely for delicate and synthetic fabrics as for more rugged linens and cottons.

A further object of this invention is to provide temperature selection in an electrically operated automatic clothes dryer without the use of an adjustable thermostat, thereby increasing reliability while decreasing manufacturing cost.

Other objects of this invention lie in increasing safety, ease of operation and temperature selection in an electric clothes dryer of the type having a tumbling basket or drum with an electric heater, and a fan for forcing heated air through the tumbling clothes.

In carrying out my invention, a feature thereof pertains to the use of an electric heater for the dryer which is divided into two independently controlled sections, adapted to be electrically connected together in parallel. A cycling thermostat in series with both heater sections limits maximum drying temperature, while a time controlled switch determines the period of operation. For manual selection of a lower operating temperature, safe for the more delicate and synthetic fabrics, a manually operable switch is provided to open the circuit of one section of the heater. The power output of the remaining heater section is selected to provide a considerably lower peak temperature within the machine, and below the temperatures held by the cycling thermostat. The dryer further includes an access door and a switch actuated upon opening of the door to terminate both motor and heater operation. Additionally, the time-controlling means provides a cooldown period during which the motor and fan are operating, but without heater operation.

The features of the invention which are believed to be novel are set forth with particularity in the appended claim. The invention itself, however, both as to its organ ization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings, in which Fig. l is a cross-sectional elevation through a clothes dryer embodying the invention with certain surfaces broken away to illustrate details; Fig. 2 is a partial rear elevation of the machine illustrated by Fig. l, with portions thereof broken away to illustrate details; and Fig. 3 is a schematic wiring diagram representing the invention.

Referring to the drawings, the invention is illustrated as applied to aclothes dryer of the domestic type enclosed in a cabinet structure including, as shown by Fig. 1, a front wall 1, rear wall 2, and top 3. The cabinet enclosure may be completed with conventional side walls 4 and 5 as illustrated by Fig. 2. The front wall l of the ldryer is provided with an access opening in which is mounted a loading ring 6. This access opening is closed by a suitable door 7 hinged to the cabinet structure. An

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air seal between door and cabinet is provided by means of diameter than the diameter lof loading ring 6. Thus, opening 12 in the basket provides access to the interior thereof for loading and unloading of clothes. A rear wall 13 of the basket is riveted or otherwise secured to a hub 14 formed on the end of a driving shaft 15. Since the basket is supported in cantilever fashion on shaft 15, it is desirable to reinforce rear wall 13 by an additional rear wall section 16, likewise secured to hub 14 and riveted as at 17 to the main rear wall section 13 of the basket.

The rotatable mounting of the basket within the cabinet is provided by suitable structural members 18, for example in the form of angle iron supports, which rest upon base Secured to this supporting structure Sleeve 20 in turn 19 of the machine. 18 is a bearing support sleeve 20.

carries front bearing 2l and rear bearing 2.2 in whichA shaft V15 rotates. A suitable clamping means 23 is provided in a manner well understood in the art for securu ing the bearing support to the supporting structure.

T o define an air chamber surrounding drum orv basket 9, an outer wrapper is provided comprising an outer curved sheet 24 extending upwardly from base 19 and around the peripheral wall of the basket, and front and rear wrapper walls Z5 and 26. The encircling wrapper wall portion 24 is covered with an insulation blanket 27; and similarly front wall 25 is covered with an insulation blanket 2S while the rear wall is insulated by blanket 29. Thus it can be seen that basket 9 is enclosed in an insulated space confining the heated air employed for evaporating moisture from damp clothes tumbling within the basket.

Air ow through the basket and rotation thereof is provided by utilizing as motive power an electric motor 30. Shaft 3l of this motor rotates a fan 32 and a driving pulley 33. Pulley 33 is belt-connected to la large idler pulley 34 having as a unitary part thereof a small idler pulley 35 which in turn is connected by belt 36 to the main driven pulley 37 keyed to shaft 15 of the basket. Idler pulleys 34 and 35 may be carried on a shaft 38 journaled in a Supporting plate 39 in a well-understood manner. designed to provide a speed reduction from motor 30 to the basket, whereby the basket rotates at a speed to cause tumbling of clothes contained therein.

Heat for drying the clothes is provided by an electric heater structure designated generally by the reference numeral 4t). While numerous electric heater constructions may be employed in accordance with the teachings of this invention, conveniently the actual heating coils 41 are carried on a series of ceramic insulators 42, which in turn are secured to a base plate and supporting structure 43. The heater assembly is closely adjacent to the periphery of basket 9 and preferably a screen 44 is provided between the heating coils 41 and the basket to avoid direct contact of lint with the heater. The entire tion with the heater assembly at least two independent heater sections having respective terminal studs '47 and f As illustrated sche- ,l

48 and a common terminal 46. matically in Fig. 3, these heater sections are and 66.

Patented Apr. 23, 1957 The idler pulley arrangement is, of course,

available-forfadju'stment byV the operator alongiwith-'ay temperature selector switch 51. The operationl of' these devices -will be'explained' more" fully v in` connection with the wiring.y diagram ofFig'; 3.

Automatic control of the dryer yis accomplished in part bytheiuseV of temperature control and safety control thermosta-ts 52 and 53 respectively as shown byFig'. 2. The temperature control thermostat 52v is: of to-cycle between on andoff peraturelwithinv the dryer. The safety cont-rol thermostat-y is normally closedan'd-isset toopenat a predeterminedhightemperature, higherthan the Vter'nperature held by thermostat 52, primarily asv a safety precaution4k For example,-` thermostat- 52- should hold a temperature in While l have not shown in detail interior wall sections within the dryer to direct the flow of air through the dryer, it is to be understood that any'of the numerous arrangements well known in the art may be employed. Preferably, the dryer includes an aircirculation system asg disclosed and claimed in the co-pending application of John H. Robinson and Paul L. Paulsen, Serial No. 209,280, tiled February 3, 1951, now Patent 2,707,837 assigned to the General Electric Company, assignee of this application. In brief, fan 32draws fresh airY in through the back wall of the dryer through a plurality of louv-res 57, illustrated by Fig. l. This incoming air passesdownwardly in the space between rear wall Z of the cabinet and the rear insulation blanket 29, through the fan blades and over the motor, and by ozone lampV 55.` A substantial portionV of the air then flows upwardly toward and over the electrical heater assembly 40 and'into the dryer basket.v The air is finally/exhausted out the front'V of the machine through a lint trap assembly 58 of conventional construction.

Referring now to Fig. 3, the motor 30 is illustrated asV including conventional run and start windings 59 and 60 along with a centrifugal switch' including contacts 61' and 62` bridged'byan armature 63 operated by centrifugal' mechanism'64.' Whilethe'm'otorl is at'rest, the' armature the type adapted` positions in a relatively narrow temperature band, thereby toy hold operating tem-l 63 bridges contacts 61 and62 to include start winding 'of 'the motor in the electrical circuit. However, as

soon as the motor has come up to speed, the start circuit is opened by the 'centrifugal mechanism. This same Vcentrifugal' mechanism closes acircuitthrough contacts 72" and 73 to'energ'ize the electrical heaters when the motor is operating at normal oi-` near` normalA speed.

The electrical heater assembly 40 `as shown vby Fig. 3 comprises' two separate and distinct heating sections V65 and" 66. These two heater sections are connected togetherat one'end by utilizing the ycommon terminal` 46; Pwer is supplied toV the'heaters at the opposite 'ends' thereof through 'separate' terminals 47 and 48' so that thehe'ater sections are in electrical' parallel. In serieswith heaterl se'c'tion'65 `is the'manually operable temperature selection 'switch' 51.

It iscUn't'emplated in accordance with this invention that when' both heater sectionsY 65" and' "66 'are operatingfswitcli 51 closed, heat' is suppliedV to 'the' dryer at a 'relatively rapid ratefto increase the temper'alt're 'thereof'and evaporate water as quickly as' possible: Under 'these'conditionc maximumdi'yer tempera-@- clothes load. However, withr heater section 6G operating4` alone, switch 51 open, it is contemplated that with a normal'clothes load amaximum temperature of only 160 F. is attained;

Fig=3ealso illustrates inV more detail the nature of the timer comprising a pair of cams 67 and 68 for actuating switches 69 and 70, respectively. These cams are driven by a timer motor 74, or they may be manually adjusted to any desired position by control knob 50a.

The components are illustrated in Fig. 3 in theVv positionsoccupiediwhen the dryer is at rest. lThe clothes o r materials to be dried are inserted into basket 9 through the access door 7. A`switch 71 is opened upon opening thedoor and isclosed upon closure of the door. This switch functions-to stop operation of the machinel whenever the door is open.

In operation, when the door is closed after loading the i machine, control knob 50a isrotated to rotate cams'jm and- 63 in a clockwise direction. This closes both switchesSand 70 to commence operation of thema-f chine: Both the temperature control and the safety control-thermostats are closed when the machine isycool,

The manually operable switch 51 may be either open .or`

closed depending-upon the desire of the operator. Until Y such time as the motor has corne up to speed, .armaturey 63 ofr the centrifugal mechanism is iny `its down position as-shown`by Fig. 3.. Electrical power is supplied to the matching-through terminals 75, 76, and 77 on a terminali blockf78- for the machine. Normally, line 76 is electricalV terminal 80 connects'. both to main'winding 59 (of the motor yand tovcontacttiZ of the centrifugal switch for the` start winding circuit. From the opposite side. of the motor windings'7 terminal 81 of the motor, the circuit is completed tlidroug'hline S2, door operated switch'71l, line'y 83, and a fuse" to the yiieut'ralterniinal 76 ofthe' power' supply. Byfthis circuit, approximately V. is'appl'edl to the Iriot'or to' 'cor'fimence its operation.

The-heater?sectionsicannot'be energized while the'motor is at'rest.n Howeveig'as soon as the' motor comes/np to' speed,` `a circuit is completed frorr'tcrrninal 75, through switch't, line 79, motor terminalfS, centrifugal switchN contact 72,"ce'ntrifu'g'al`mechaiiism`armature 63,A contact 734,to'wcommonterminal lti'ofv the heating elements.v From"terriiinals 47' and' l-Sfof the heaters, the circuit is completed through ythe safety control thermostat`A 513k, tem'- perat'ure'control thermostat S2, lineV SS, timer switch 619,1l to theoppsite side of'tlie line '77. Thusyboth heating elements are ene'rged if'the manually operableswitch 51V is cls'e'd'an'd the'mt'o is'operating'. If the temperature selectoiswitch 51' is open, only one section otthe'heaterv is effective. c c Y y n rlhe timer motor is `energized and is effective' to rotate* cams 67 and k68`upo`ncommencemeiitiof operation a circuit commencing withter'minal '75 and continuingL throiighmswitch and'a line 86 to one terminaliof the plct'es its circuit"through'line 0F/,to line 82;, the'doorV operat'edwswitchs-l'lfthe line 83 to the electrical neutral temperature within the dryer rises to the maximum temperature determined by the setting of the cycling control thermostat 52. As previously explained, this thermostat holds the temperature within the dryer to a range such as 190 F. to 210 F. If the temperature control switch 51 remains open, however, the temperature in the machine under normal circumstances would rise only to approximately 160 F.

The timer motor continues to rotate cams 67 and 68 to the point in the cycle where lswitch 69 opens the circuit to the heating elements. However, at this point switch 70 remains closed under the inuence of cam 68 to continue the motor in operation for a period of time without `operation of the heating elements. Subsequently, the complete cycle of operations is terminated by opening of switch 70, which not only terminates operation of motor 30, but also operation of timer motor 74.

If at any time during operation of the machine an abnormally high temperature occurs for any reason whatsoever, the safety control thermostat 53 opens the circuit to the heating elements.

In accordance with this invention, it is contemplated that both thermostats 52 and 53 are of the type pre-set upon manufacture to actuate at a particular temperature. No adjustable feature is needed for either of these thermostats. Itis found in practice that a more reliable thermostat can be provided if the adjustable feature can be omitted. However, temperature control of the dryer is still achieved by the use of independently controlled parallel sections in the heater Winding, which sections are under the control yof one or more manually operable switches. While I have shown the complete heating element assembly as including only two sections, with one manually operable switch, it can be readily understood that additional sections and additional switches for control thereof may be added as desired.

While this invention has been described by reference to a particular embodiment, it is to be understood that numerous modications may be made without actually departing from the spirit of the invention. It is therefore aimed in the appended claim to cover all such equivalent variations as come within the true scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

A clothes dryer comprising a tumbling basket, air circulating means for circulating air through said tumbling basket, a motor for rotating said basket and driving said air circulating means, electrical heating means including a basic heater section and an auxiliary heater section and positioned in the path of at least a portion of the air circulated by said air 4circulating means, means forming parallel electrical circuits for said heater sections, a cycling temperature control thermostatic switch in electrical series with both heater sections to limit maximum temperature within the dryer when both basic and auxiliary heater sections are in operation, a time controlled switch in series circuit relation with both sections of said heating means, and a manually controlled temperature selector for independently controlling said auxiliary heater section, the energy output of said basic heater section providing insuicient heat to heat said air to a level effective to actuate said cycling control thermostatic switch.

References Cited in the tile of this patent UNITED STATES PATENTS 2,398,880 Broglie Apr. 23, 1946 2,515,427 Schulze July 18, 1950 2,550,118 Kauffman Apr. 24, 1951 2,621,423 Clark Dec. 16, 1952 2,623,979 Shewmon Dec. 30, 1952 2,707,837 Robinson et al. May l0, 1955 

